A critical review of the Water Sorptivity Index (WSI) parameter for potential durability assessment: Can WSI be considered in isolation of porosity?

ABSTRACT The Durability Index (DI) approach used in South Africa is linked to transport-related properties of the cover layer of concrete. This performance-based approach utilises three different durability-related parameters, namely Water Sorptivity Index (WSI), Oxygen Permeability Index (OPI) and Chloride Conductivity Index (CCI). In the water sorptivity test, both the sorptivity and the water-penetrable porosity of the concrete are measured. Until now, porosity has not been considered directly as a separate durability-related parameter. This paper analyses these implications and suggests that porosity should be adopted as a further index. The paper concludes that sorptivity cannot be interpreted without also reflecting the porosity value since these two parameters are inter-related. Keywords: concrete durability, durability index, water sorptivity, porosity, absorption